The present invention relates to tape transports and particularly to apparatus for causing movement of a magnetic recording tape relative to a recording and/or playback head. More specifically, this invention is directed to an improved tape drive system in which the tension imposed on the tape is a lower average tension and more uniform tension from beginning of tape (BOT) to end of tape (EOT).
Tape transport mechanisms are, of course, well known in the art. Tape transports of the same general type as that to which the present invention is directed are exemplified by the apparatus disclosed in U.S. Pat. Nos. 3,620,473, 3,974,982 and 4,455,001 which are assigned to the assignee of the present invention. A tape transport will typically include a tape handling mechanism, a magnetic tape on which a program may be stored, a read/write head and a drive motor. One type of tape drive system employs a peripheral drive belt to drive the tape packs. The belt is arranged to run in a path which contacts the tape packs, and the belt is driven by a capstan. A typical peripheral belt drive system may have a spring loaded idler to apply tension to the drive belt and a brake to establish a differential rotational velocity of the tape to establish a necessary tape tension to maintain the tape in contact with the read/write head and avoid tape spillage.
A particular problem with the prior art relates to the absolute levels of tape tension and the average tape tension from BOT to EOT. However, in practice, the tape tension increases significantly at the beginning of the tape and at the end of the tape, and the average tape tension is higher than the desired constant level The high tension levels at BOT and EOT cause stresses which, in severe cases, can distort the tape. Moreover, the increased average tape tension results in wear of the tape and the read/write head, wastes power in that more input power is required to drive the unit, and generally results in less than ideal transfer of tape from reel to reel.